Well surveying apparatus



Nov. 27, 1962 A. LuBlNsKl WELL sURvEYING APPARATUS 2 Sheets-Sheet 1 Filed Dec. 29, 1958 ARTHUR LUBINSKI INV ENTOR FIG.

AT TURNE Y Nov. 27, 1962 A. LuBlNsKl WELL sURvEYING APPARATUS 2 Sheets-Sheet 2 Filed Deo. 29, 1958 FIG. 4

ARTHUR LUBINSKI FIG. 6

ATTORNEY 3,065,633 Patented Nov. Z7, 1962 3,065,633 WELL SURVEYING APPARATUS Arthur Lubinski, Tulsa, Okla., assigner to Pan American Petroleum Corporation, rTulsa, Ghia., a corporation of Delaware Fiied Dec. 29, 1958, Ser. No. 783,494

' 7 Claims. (Cl. '73-151) 'This invention relates to an apparatus for determining the deviation of a hole from a straight line. More particularly, it is directed to an apparatus for logging a well to determine the crookedness or rate of change of deviation therein and to ascertain the stress to which well apparatus, such as drill pipe, casing, tubing, and sucker rods, is or will be subjected.

Numerous devices have been proposed for determining the inclination of a well. While some of these devices are adapted in the broad sense to produce a continuous log of the inclination and direction of a well, in practice the most successful and, therefore, the most Widely used instruments are essentially single-shot or multiple-recording single-shot devices which produce a record of the inclination of a well at a multiplicity of points. All of these logging devices are suiiiciently accurate for the intended purpose; namely, determining the deviation of a well from vertical and the vertically projected position on the lease of a point in a well. We have found that with inclination-measuring devices of this class, regardless of the spacing of the readings, it is virtually impossible to determine the angularity or crookedness of a well, i.e., the flexure or bending of a well from a straight line. We have also found that while the inclination of a well and the vertically projected position of the bottom of a well on a lease are important in many respects, the crookedness or rate of change of direction are much more important in some respects. For example, it has been found that the wear, and particularly stress, strain, and failure of well apparatus, such as drill pipe, casing, tubing, and sucker rods, are substantially independent of the inclination of a well when the inclination is within a reasonable range. The destruction, i.e., the wear and failure of such well apparatus, is instead dependent more upon the crookedness or rate of change of inclination than upon the inclination itself. This parameter, i.e., the crookedness of a well, cannot be satisfactorily determined with any of the well-logging devices now used.

We have found that both the bending stresses in and the lateral forces on a well conduit or rod located in a crooked, i.e., non-linear, section of a hole increase with the tension to which the conduit is subjected, such tension obviously increasing with the length of pipe suspended below that section. When such well apparatus is located in a shallow hole, it is not subjected to a large tension. 'The tension at that same depth, however, increases as the length of the conduit or rod increases. In other words, a non-straight section of hole will not necessarily damage a drill pipe as that section is being drilled or soon after it has been drilled, but only at a much later time when the pipe in that section is under a much greater tension due to the weight of the pipe suspended below the crooked section. Any remedial work such as teaming or plugging back and sidetracking should, however, be undertaken as soon as possible after damaging crookedness is discovered. In the past it has been impossible, as a Section of a Well was being drilled, to ascertain Whether the crookedness at that section might later cause damage to a drill pipe or pumping equipment therein so that remedial measures might be taken to straighten the hole at the proper time, i.e., before the hole has been drilled much deeper.

It is, therefore, an object of this invention to provide an improved well-logging apparatus. It is a more specific object of this invention to provide an elongated apparatus adapted to be run into a hole to determine the crookedness of the hole. In its more specific aspects, it is an object of this invention to provide an apparatus for ascertaining the stresses which will be placed in well apparatus due to changes in direction or crookedness of a well by logging the well Iwith a simulated well apparatus under simulated operating conditions. Other objects of this invention will become apparent from the following description. In this description reference will be made to the accompanying drawings in which:

FIGURE l is a vertical View partially in cross section of an apparatus for measuring the flexure of a hole in the ground;

FIGURE 2 is a view partially in cross section of a modication of the apparatus shown in FIGURE l;

FIGURE 3 is a View partially in cross section of another embodiment of a well-logging apparatus in accordance with this invention;

FIGURE 4 is a wiring diagram for use in the apparatus shown in FIGURE 3;

FIGURE 5 is a cross-sectional view of a preferred embodiment of a Well-logging apparatus; and

FIGURE 6 is a cross-sectional view, taken along the line 6 6, of the apparatus shown in FIGURE 5.

This invention, in brief, may be described as a device for logging a well to determine throughout the well or a section of the well either its crookedness, i.e., its deviation from a straight line, or the detrimental effects of crookedness, i.e., bending stresses and lateral forces. The logging apparatus which is lowered into the Well is preferably scaled to simulate well apparatus and means are provided for indicating the strains due to hole crookedness in the simulated well apparatus as it passes through the well and as an indication of the stresses, both bending stress and that due to lateral forces, to which in operation the actual well apparatus is to be or will be subjected.

Referring now to FIGURE l for a more detailed description of one embodiment of an apparatus for determining the crookedness of a hole and an indication of the eventual stresses to which a well apparatus will eventually be subjected, the part of the probe or logging device lowered into the hole consists generally of an elongated upper section 10 and an elongated lower section 11 ilexibly connected at their adjacent ends by a universal or ball joint 12. This probe is shown located in a bend in a hole in the earth, viz., a Well 13. The lower head 14 is preferably cylindrical and is coaxially mounted on the bottom end of a long rod 15. The lower section 11 and, therefore, rod 15 may be of any desired length, typically between 5 and about 30 feet, but, as shown hereinafter, in the preferred embodiment the length of this lower section and the length of the upper section are each desirably substantially equal to the length of simulated joints of an actual well apparatus. The flexible or elastic connection, ball joint 12, between the upper and lower sections includes a ball 16 on the upper end of rod 15 mounted in a socket 17 on the lower end of the upper section Iii so that the lower section is free to move laterally in any direction which results in an angle (the average angular change in direction of the hole between the ends of the device) with reference to the upper section. An arm 18 coaxial with rod 15 is connected to the ball 16 opposite the rod and protrudes into the housing 19 which is connected to the lower end of tubing 20. A segmented spherical commutator 23 having a multiplicity of concentric insulated metallic rings 24 is mounted in housing 19 coaxially with ball 16 and tubing 2t) so that a brush 22 on the upper end of arm 18 separately contacts each of the concentric rings. Each of these rings is connected via a separate conductor 25 within suspension cable 26 to an instrument, either indicating or recording, preferably a recording galvanometer, which is located at the surface. This instrument (not shown) then indicates the concentric ring 24 with which the brush 22 is in Contact as an indication of the apex angle or angularity in any direction of the lower section 11 with respect to the upper section 10. A helically wound resistance may be substituted for the concentric ring commutator in some cases as is well known in the art. Suitable centering devices such as leaf springs (not shown) may be placed on the lower head 14, the housing 19, and the upper head 21.

In operation, the subsurface logging apparatus is lowered into the well on suspension cable 26 and the deviation of the hole from a straight line versus depth of the logging .device is recorded. From this deviation record it is then possible to determine the bending moments and lateral forces which may be encountered in the actual apparatus so that, if necessary, steps can be taken to straighten the hole or design the well apparatus to mini? nn'ze the adverse effects of the hole crookedness.

In the embodiment of the logging apparatus shown in FIGURE 1, the log is typically stepped at, for example, one or more degrees of angular change in direction. It is desirable in some cases, however, to have a continuous record without these steps so that crookedness can be determined more accurately. The spiral potentiometer described above may obviously be substituted for the commutator to produce such a result. A modification of the apparatus shown in FIGURE l which produces such a continuous log is shown in FIGURE 2. In this embodiment a follower 27 is concentrically and slidably mounted in a support 28 within the housing 19. This follower which is shown with a conical lower surface is urged downward by a compression spring 29 so that the lower surface 31 contacts the upper end of arm 18. A strain gauge 32 which is electrically connected to a single conductor 25' in suspension cable 26 is anchored at the upper end to an upper support member 33 and is connected at the lower end to the follower 27 so that the length of the gauge and, therefore, its restivity or output is dependent upon or a function of the vertical position of follower 27.

The operation of this modification is similar in many respects to the operation of the embodiment shown in FIGURE l. In this case, however, when there is no deviation in the hole, the upper end of arm 18 is at the apex 34 of the conical lower surface of follower 27 and the follower is held in its lowermost position by spring 29. This places a maximum tensile stress in the strain gauge 32. As the deviation of the hole increases, the upper end of arm 18 is moved laterally away from the apex 34 and the follower is raised, the amount depending upon the angularity or crookedness of the hole and the contour of the lower surface 31. -While this lower surface is described as a conical surface, it will be apparent that other contours can be employed to produce a vertical movement of follower 27 or an electrical output from strain gauge 32 which is proportional to some function, e.g., a straight line, logarithm, or square root function, of the angularity of rod 15 with respect to tubing 20.

Reference will now be made more specifically to FIG- URE 3 for a description of another embodiment of our subsurface logging apparatus which, in addition to producing an indication of the crookedness of a well as shown in the embodiment of FIGURE l, is adapted to `be scaled to measure directly the strains in a simulated well apparatus due to crookedness of the well as an indication of the stress in and lateral force to which actual well apparatus will be subjected when it is subsequently placed in the well. The upper section 1t) and the lower section 11 are in this case more or less rigidly joined at their adjacent ends by a simulated coupling which nevertheless has some deformation under stress. Since it is impossible to scale down the well and, therefore, the length of these sections in order to simulate actual conditions in a well, the geometry of each of these sections and any additional sections joined thereto is desirably equal to that of an actual joint of drill pipe or other well apparatus being s'mulated. Thus, the length (L) of each of these sections is typically in the case of sucker rods 25 feet and in the case of tubing or drill pipe about 20-30 feet. The outside diameter (d) of the lower tubular membei' 35 and the upper tubular member 36 and the outside diameter (D) of the simulated tool joints or couplings 37, 33, and 39 are also typically equal to the respective diameters of the actual well apparatus being simulated. These same geometrical considerations apply to the apparatus of FiGURE l in that the diameter of the simulated couplings, i.e., heads 14 and 21, the diameter of the housing 19 and the diameter of the simulated rod, may be varied so that the clearance between them and the well wall or the wall of a conduit simulates the clearance available in the actual well apparatus as a more accurate indication of the stresses to which an actual well apparatus will be subjected. For example, where it is desired to simulate the stresses in sucker rods before the tubing and casing have been installedl in a well, the simulated couplings and rods are made large enough so that the differences between their diameters and the diameter of the well are substantially equal to the clearance between the actual well apparatus, including sucker rods and sucker rod boxes, and the tubing. Under these conditions it can be seen that for any given length of an actual and a simulated well apparatus, the logging apparatus simulates the actual well apparatus, i.e., the neutral axis or elastic line in the two are of substantially the same shape and the bending moments in and lateral forces in or reactions on the simulated apparatus are reduced in a known ratio when To Eule ESIe where:

Since, as indicated above, the length of each of the upper section 1G and the lower section 11 is generally determined by the length of the joints or sections of an actual well apparatus, the simulated apparatus or logging probe is typically at least as long as two joints of the actual well apparatus and may be as long as 3-4 or more joints of the actual well apparatus. While there is a limitation on the length and outside diameters of the probe, the material in and the internal diameters of and tension in each of these tubular members may be varied over a wide range provided only that the ratio to TS/ESIS should always for any particular well at any particular depth be constant and substantially equal to the ratio of Ta/Eala. Under these conditions it can be seen that the strain and accordingly the stress in an actual well apparatus can be determined by direct measurement without using the actual well apparatus itself by reducing Ts and one or more of the other parameters in the logging apparatus. The weight suspended from the logging device can thus be reduced and it can be placed in a short section of a hole available before drilling is completed and yet permit simulation of a full length well apparatus. An additional advantage is that the device can, if desired, be lowered into a well on a light suspension cable. The tension in the logging device can be controlled so that it simulates the tension in a section of actual Well apparatus at any location in a rod or pipe string by connecting a weight 41 to the bottom simulated coupling 37. The amount of this weight depends upon the location of the test section in the hole, i.e., the length of actual apparatus to be supported below the elevation at which the log is made. The weight 41 is desirably adjusted from time to time so that it simulates within about plus or minus the weight of actual well apparatus below a section of the hole. That is, after a particular weight has been attached to the lower end of the logging apparatus, it is run into the well and a section of the Well, desirably a section less than about 10% of the length of the well when completed, is logged. The probe is then removed and, after further drilling, another weight is substituted if needed, the magnitu-de of the new weight depending upon the position or elevation of the next section in the well to be logged relative to the depth or contemplated depth of the well. The device with the new or changed weight attached is then lowered into the well to log a second or subsequent section of the well. While a weight is used in the preferred embodiment to place tension lin the logging device, it will be apparent that other means, either xed or variable, of stressing `the logging device in tension, eg., friction devices which grab the well wall, may be substituted. Similarly, the material or a combination of materials forming the tubular members 35 and 36 and the simulated couplings 37, 3S, and 39 can be selected to produce any desired elasticity and Youngs modulus. For example, materials such as plastic and rubber or combinations thereof with reinforcing metals are preferred. Also, the moment of inertia with respect to a diameter of each of the tubular members may be varied by varying the inside diameter and the wall thickness of the member. With all of these variables it is apparent that various means are available for reducing the weight of the subsurface logging probe while maintaining the ratio T ,/E .,Is constant. when the logging device is constructed of a combination of materials, such as steelreinforced-rubber, then the expression ESIS should be construed as the flexural rigidity of such a combination.

In order to determine either or both the bending moment and the lateral reaction of the wall of the hole on the logging device and the corresponding parameters for the actual well apparatus, means are provided for determining the maximum strain longitudinally and/ or laterally at various points on the periphery of the probe, particularly at or adjacent to or in the area of the center coupling 38 which may be considered flexible or elastic in that it deforms under stress, the amount of deformation depending upon the crookedness of the hole, the tension in logging device, etc. Electrical transducers such as bonded wire, electrical-resistant strain gauges are mounted on the probe at points of maximum stress such as at the center of simulated coupling 38, at a midpoint and at the lower end of the tubular members 35 and 36, respectively. The gauges are oriented to indicate strain either laterally or longitudinally in the probe or both laterally and longitudinally. A signal indicative of the resistance of these strain gauges is then either transmitted to the surface through the suspension cable 26 on which the logging device is run into and withdrawn from the well or recorded within the device. In one embodiment each of these strain-measuring elements is separately connected by an electrical conductor 25' to a metering device at the surface so that each produces a continuous log of the strain in the material at the point where the gauge is bonded to or otherwise embedded in the surveying apparatus. In a preferred embodiment, however, each of the gauges is connected to a circuit within the enclosed container 43 by which the output from each is periodically and in series transmitted via a single conductor to the surface or by which the output of the gauge under maximum strain is transmitted selec- 5 tively to the surface via the single conductor within the suspension cable 26.

A circuit suitable for producing a signal indicative of the maximum strain at any one of the transducers is shown in FIGURE 4. Each of the strain gauges 42 is connected in a balanced bridge circuit 44. The bridge circuits are in turn connected in parallel to a power supply 45 which is preferably a battery. An alternating current generator may be substituted. In any case the output signal from the various bridges, i.e., the unbalance due to distortion of the strain gauges 42, is amplified in the various ampliers d6. The amplified signal from each of the amplifiers is then sent to an or circuit comprising the diodes 47 connected in series with biasing resistor `43 and battery 49. Whenever any one or more of the strain gauges is distorted suiiiciently to produce an amplifier voltage output greater than the bias voltage of battery 49, the diode in that particular branch of the circuit emits a signal, the amplitude of which is proportional to the distortion of the strain gauge. This signal is then transmitted to a recorder either within the probe or via cable 26 to a recorder or other indicator at the surface. If desired, this amplitude modulated signal can be converted to a frequency modulated signal within the well and the frequency modulated signal can be transmitted via the cable 26 to a suitable frequency meter at the surface.

A self-contained logging device or probe which may be used to produce a record of bending moment to which an actual well apparatus will later be subjected, and therefore of hole crookedness, is shown in FIGURES 5 and 6. In this embodiment the upper section l@ and lower section 11 comprise primarily metal-reinforced rubber tubes in which a number of longitudinal wires 5l are embedded in rubber tubes. The logging device is run on a cable 26' which in this case is not used to telemeter the signals from the probe to the surface since the recorder is self-contained. The cable 26 is connected via a perforated cap S2 to the upper head or simulated upper tool joint or coupling 39. The upper tubular member 36 connecting this upper coupling and the center coupling 38 has a recorder 53 at a midpoint, preferably about l-S feet above the center coupling. The lower section 11 includes the lower rubber tubular member 3S', which is also preferably longitudinally metal reinforced as indicated in FIGURE 6, a lower tool joint or coupling 37 and weight 4l connected as by threads to the lower coupling.

The recorder is held in position by bands 54 around the rubber tubular member. A circumferentially elongated hole 55 in the rubber tube and a circumferential slot 56 in the recorder housing 57 permit the insertion of a record plate 58 in the recorder. This record plate desirably has a chart on the lower side which is scratched or otherwise marked by the stylus 59. |This stylus on the arm 61 is mounted on and guided laterally by the center coupling 38 to which it is affixed at its lower end through the perforated frog 62. The stylus is held against the chart by a compression spring 63 within a recess in the upper end of arm 61. Due to the similarity, i.e., the correspondence of external geometrical dimensions, between the probe and the actual well apparatus, the probe is distorted exactly as the actual well apparatus. As the probe is passing through a crooked hole, the upper end of the stylus moves laterally and describes a path on the chart indicative of the bending moment in the actual well apparatus or more exactly of the average bending moment over an area equal to the length of the short section 64 of rubber tube. For an exact correlation of the log with depth, in one embodiment the chart is first radially subdivided in equal time intervals and then rotated as by a clock.

In operation after the record plate 5S is inserted in the recorder and the proper weight is suspended on the lower end, the self-contained logging device is lowered into the well to the desired depth and then withdrawn. As the device passes through the well, it makes a continuous record on the chart of the lateral displacement of the stylus from the null position. When the device is returned to the surface and the chart is examined, it can be determined whether the crookedness or deviation of the hole is as great as or greater than the permissible bending stress level by observing the maximum deflection of the stylus on the chart. If desired, several runs can be made to isolate the section of the Well having excessive crookedness. Obviously, also, it may be desired in some cases to provide means to disengage the stylus from the chart except while a selected interval of a well is logged.

The maximum flexure or strain at any of a number of points in the logging device is thus continuously indicated or recorded either at the surface or within the logging device. This strain, as indicated above, is indicative of the hole Crookedness through which the logging device is passing and is desirably correlated with depth by suitable depth-measuring means connected with suspension cable 26 as is well known in the art. This strain or signal produced by the strain is furthermore and most importantly a direct indication of the effect of crookedness, viz, the bending stress in or the lateral force on the device or both the bending stress in and lateral force on the device. This record or log may also be compared with known or established standards or calibrated to read directly the hole crookedness or the stress to which actual well apparatus will ultimately be subjected. Remedial steps to overcome or remove undesirable crookedness, dog legs, or the like, can then be taken as desired.

From the foregoing it can be seen that while the logging apparatus has been described with reference to certain preferred embodiments, various modifications therein can be made without departing from the spirit of the invention. This invention should, therefore, be construed to be limited not by the description but only by the scope of the appended claims.

I claim:

1. An apparatus responsive to crookedness of a well at depths substantially above the well bottom comprising an elongated elastic member having two sections of substantially equal length each approximating the length and diameter of a joint of well apparatus having enlarged end couplings, enlarged portions at each end of said member of a diameter approximating the diameter of said couplings, an enlarged central portion on said member of a diameter approximating the diameter of said er1- larged end portions and about midway therebetween, means at least in part attached to said central portion and responsive to the iiexing of said member in the vicinity of said central portion, a suspension cable attached to one end of said member for moving it in a well, and means attached to the other end of said member for stressing it in tension suliciently to affect the flexing of said member in the vicinity of said central portion due to the crookedness of a well in a manner indicative of the flexing of said well apparatus by said well crookedness and by the weight supported by said well apparatus at the depths where said crookedness occurs.

2. An apparatus as in claim l, wherein said flexingresponsive means comprises a plurality of bonded strain gauges on said enlarged central portion, and including means to indicate the response of that one of said gauges subjected to maximum deformation.

3. An apparatus as in claim 1, wherein said flexingresponsive means comprises indicating means attached to said member at a point spaced from said central portion by a short length of said elastic member, and contacting means attached to said enlarged central portion and extending through said short length of member into contact with said indicating means to indicate thereon the flexing of said short length of member.

4. An apparatus as in claim 1, in which said memberstressing means comprises a weight scaled to produce in said elongated elastic member exing which is indicative of the flexing of a weight-supporting well apparatus to be subsequently placed in said well at about the depth of an indicated well crookedness.

5. An apparatus for simulating the strain due to well croolcedness in an actual sucker rod string, including sucker rods and sucker rod boxes, before said actual sucker rod string and a well conduit therefor are installed in a well comprising an elastic upper member having a length substantially equal t0 an actual sucker rod, an elastic lower member having a length substantially equal to an actual sucker rod, a coupling connecting said upper and said lower members, simulated couplings at each of the outer ends of said connected members, the difference in diameter between said couplings and said well being substantially equal to the difference in diameter between said sucker rod boxes and said conduit, the difference in diameter between said members and said Well being substantially equal to the dilerence in diameter between said sucker rods and said conduit, a weight attached to the lower end of said lower elastic member for stressing said members in tension by an amount proportional to the stress on an actual sucker rod at the depth of positioning said apparatus for a strain measurement, strain gauge means connected to at least one of said coupling and said members to produce a signal which is a function of the strain in at least one of said coupling and said members, means to record said signal, and suspension means connected to said upper member for lowering said members and said couplings into a Well.

6. An apparatus for simulating the strain in a jointed actual well apparatus comprising an elongated probe member having a length at least as great as two joints of said actual well apparatus, enlargements on said elongated member simulating the spacing and diameter of couplings on said actual well apparatus, weight means connected to one end of said elongated probe member for stressing said member in tension, suspension means connected to the other end of said elongated member for lowering said member into a Well, at least one strain gauge on said elongated member in an area of maximum flexure, the output of each of said at least one strain gauge being a function of the strain in said tubular member in that particular area, and means to record a signal which is a function of the output of the one of said strain gauges which is located at said area of maximum strain, the dimensions of said tubular member and the amount of said weight means being scaled so that for any given length of the probe member and actual well apparatus the quantity T a/ EB] a is substantially equal to the quantity T ,nssls Where:

Ta=tension in said actual well apparatus.

T s:tension in said probe member.

Ea=Youngs modulus of elasticity for the material in said actual well apparatus.

Es=Youngs modulus of elasticity for the material in said probe member.

la=moment of inertia of said actual well apparatus about a diameter.

ls=moment of inertia of said probe member about a diameter.

7. An apparatus for simulating the strain in a jointed actual well apparatus having a multiplicity of substantially equal-length joints comprising a simulated welllogging apparatus `in the form of an elongated tubular member having at least two sections each equal to the length of one of said joints, a coupling joining said sections, enlargements including said coupling on said tubular member spaced a distance equal to the length of said joints, weight means connected to the lower end of said tubular member for stressing said member in tension,

suspension means connected to the upper end of said tubular member for lowering said simulated well apparatus into a well, a multiplicity of electrical strain gauges each bonded to a separate point on the periphery of said simulated well apparatus so that the resistance of each of said strain gauges is a function of the strain in said simulated Well apparatus at that particular point, and means to produce a signal which is a function of the output of at least the one of said strain gauges which is located at the point of maximum strain in said simulated well apparatus, the diameter of said sections and said enlargements and the amount of said Weight means being scaled so that the quantity for any length of said joints Ts/Esls where Ta=tension in said actual well apparatus.

Ts=tension in said simulated well apparatus.

Ea=Youngs modulus of elasticity for the material in said actual well apparatus.

Es=Youngs modulus of elasticity for the material in said simulated Well apparatus.

Ia=moment of inertia of said actual well apparatus about its diameter.

ls=moment of inertia of said simulated well apparatus about its diameter.

References Cited in the file of this patent UNTED STATES PATENTS En Dean et al May 13, 1958 Arps Mar. 29, 1960 FOREIGN PATENTS 14,780 Great Britain Apr. 6, 1916 

